A conventional umbrella rib assembly as pivotally secured to a central shaft of a multiple-fold umbrella is generally made of metallic material such as iron or steel, in which a rib may be pressed or processed to form a longitudinal groove from a surface of the rib adapted for receiving another neighbor rib when folding an umbrella in order for reducing the volume of a folded umbrella.
However, a conventional metallic rib is pressed by mechanical processing method to form a single U-shaped groove as recessed from a single side of the rib, rather than double grooves respectively recessed in two opposite sides of the rib. Therefore, a central rib can not receive two neighbor ribs disposed on two opposite sides of the central rib for largely minimizing a folded volume when closing the umbrella from its opening state, thereby being unable to greatly minimize a folded umbrella to be a mini compact structure.
A conventional multiple-fold umbrella as taught by Yang (the same inventor of this application) in his U. S. Pat. No. 4,739,783 and 4,676,262 disclosed a spring rib or link slidably received in a U-shaped rib groove of a base rib requiring a helical spring (as numeral "83" in U. S. Pat. No. 4,739,783) or collar (as numeral "51" in U. S. Pat. No. 4,676,262) formed in the rib groove for limiting the spring rib or link during the sliding movement within the U-shaped groove of the base rib.
However, the helical spring (83) or the collar (51) in the two prior arts shall require, further processing for embedding the helical spring (83) in the rib groove or by pressing the rib to form the collar (51), causing production inconvenience and increasing production cost. If the helical spring (83) is loosened from the base rib or the collar (51) deformed on the base rib, it will lose its effect for limiting the spring link slidably held on the base rib.
The present inventor has found the drawbacks of the conventional umbrella rib assembly and invented the compactly molded rib means.